Thinning effects on tree mortality and snag recruitment in western Oregon

Tree mortality shapes forest structural development and the resulting dead wood provides habitat for many species. However, the eff ects of thinning on mortality and large snag recruitment have been variable and remain poorly understood. We examined thinning eff ects on tree mortality at eleven Density Management Study (DMS) sites in western Oregon. Th inning reduced mortality rates for small trees, especially Douglas-fi r (Pseudotsuga menziesii), but had little infl uence on mortality of large trees (��50 cm dbh). Gaps created by harvest did not result in increased mortality during the sampling period (6 to 11 years following gap creation). Few large snags (��50 cm dbh) were produced regardless of treatment. Th inning likely reduced ongoing suppression mortality of small trees, but in the short-term did little to provide the large snags that are characteristic of latesuccessional forests. Large snags may be created in subsequent planned thinning entries, but low mortality after the fi rst thinning implementation suggests that active creation of large snags may be necessary to accelerate their development.